The discussion about the age and condition of those mummies is discussed in Scanning the Pharaohs by Hawass and Saleem (2016).

I know ZH is not the most popular Egyptologist here, but the forensic descriptions seem to be by Saleem

Earlier description by Mark Papworth as reported by Ryan
This can be found on pg 134:
KV 21A: This mummy is in very poor condition. Quote:"The missing skull, cervical vertebrae, and visible diagnostic bony elements make it difficult to discern the stature and the age of the mummy beyond general impression." The mummy is said to likely represent a female probably more than 25 years old and of medium height and a slender build.

KV 21B: There is a longer description as this mummy is somewhat better preserved (but still much damaged).The rough estimate given suggests KV 21B is probably older and somewhat taller than KV 21A.

CT Scan results (Saleem)
pages 136-141 a very short summary:
KV 21A: The headless mummy is very poorly preserved.
Quote: "It is formed of incomplete body parts that belong to at least two identities assembled incorrectly in several places."

The report stated that appearance of the pelvis suggests (emphasis mine) this is a female. Based on the femur the individual is aprroximately 1 m 48 cm (plus/minus 2.5 cm)

The epiphyseal union of the bones suggests this is a mature individual older than 21 year of age. A lack of significant age related degenerative signs indicates that this person was likely still relatively young when they died.

KV 21B: The mummy is poorly preserved and several parts are missing.
The fractured pelvis and skull make it difficult to assign gender. The morphology of the remaining cranial and facial bones suggest this may be a female.

The epiphysial union of the bones suggest this is a mature individual. The presence of mild to moderate degenerative changes in the spine and joints (signs of arthritis) indicate this person is older and may be closer to 45 years old.
This person was approximately 1 m 51 cm plus/minus 2.5 cm based on femoral length._________________Math and Art: http://mathematicsaroundus.blogspot.com/

I find it interesting that the report is very careful. The genders are tentatively identified as female.
The KV 21A has at least two identities represented? That would be a problem with any DNA testing then, wouldn't it?

The age estimates are similarly very tentative. It seems that tentative ages are given as older than 21 but relatively young for KV 21A and a relatively older age of 45 for KV 21B.